1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly relates a semiconductor device having a penetration electrode penetrating through a semiconductor substrate.
2. Description of Related Art
A semiconductor device including a plurality of semiconductor chips stacked with one another is generally referred to as a COC (Chip-on-Chip) device. The COC device is efficient in implementation due to small in size, and can make the length of lines between chips very short. Therefore, such structure is employed particularly in semiconductor devices such as memory modules, which are required to be small in size and at low costs. In a COC type semiconductor device as disclosed in Japanese Patent Application Laid-Open No. 2000-311982, through-holes are so provided as to pass through semiconductor chips. In the through-holes, a conductive layer is formed. Moreover, on a top and a back surface thereof, electrode pads (bumps) are formed, respectively. A plurality of semiconductor chips are stacked in a semiconductor device. As a result, via the conductive layer (so-called penetrating electrode) in a through-hole and the electrode pad (bump), an upper and lower semiconductor chips are electrically connected.
In a semiconductor device stacked with a plurality of semiconductor chips and provided with penetrating electrodes, the chips could be warped due to thermal stress during implementation. Japanese Patent Application Laid-Open No. 2010-161102 discloses the structure aimed at curbing an impact of such warping.
However, the above-described conventional techniques can cause plastic deformation of electrodes, the details of which will be described later, during stacking, heating and pressing. As a result, the positions of chips in a bump joint section may change and electrical connection troubles between the semiconductor chips may occur. Further, the warping of chips by thermal stress can cause a resin material (called as “underfill”), which fills the gaps between the chips, to separate from the chips.